I am onboard with everyone else. Don't care for clones, but it is nice. With all I see, yep, looks to be a fair price for what you are getting. The Mickey Thompson Cross Ram is a rare piece to find nowadays. They don't go cheap either.
You stated "new power operated convertible top." Is this a true convertible? Did you verify the vin numbers? You can buy all the parts to make a HT into a convertible. If you check the frame, the side rails should be "boxed" (closed in, not an open channel) and an additional frame/body mount about where the door is - geeteeohguy can tell better then me on convertibles.
I would verify that its a 428 as too easy to say it is when its not. Not saying this isn't. Real fast ID is the "pyramid lug" at the top back of the engine block next to the distributor, passenger side (421 & 455CI also had these). Check the block letter code. A 421CI can be bored over to make a 428CI as well. Also confirm the head casting numbers (2 digits) at the center exhaust port.
Keep in mind that a true 428CI will have a high compression ratio if it has not been changed (ie pistons with a larger dish) during the rebuild. You will have to run premium or better to avoid detonation problems. Could be costly on long drives. I would also ask about this 'cuz its going to suck up the gas.
My Opinion based on my cheap ways - With all the engine, trans, brakes, suspension, etc. improvements, I think $25K is at the high limit, but something closer to 20K would be ideal. If you plan on owning it long time, $25K would be justifiable. If you think you might flip it or sell it, then you may be taking a gamble. But it sure does look good and nothing like a top down cruise down your local avenue catching gears!